The present invention relates to skylights, and more particularly to tubular skylights, which include a reflective tube extending downwardly from the dome.
Tubular skylights have acquired increasing popularity as a means of introducing natural light into a building interior. These skylights include a dome mounted on the building roof, a light diffuser mounted in the building ceiling, and a reflective tube interconnecting the dome and the diffuser. Natural light entering the skylight through the dome reflects downwardly through the tube to the diffuser. The tube in a sense acts as a gigantic optical fiber. Typically, the domes are fabricated of acrylic; and the tube is fabricated of reflective aluminum. A tubular skylight of this type is sold by ODL, Incorporated, the assignee of the present invention, under the trademark EZ LIGHT.
The efficiency of such skylights (i.e. the amount of natural light reaching the building interior) is primarily a function of the amount of light passing through the dome into the tube and of the reflective efficiency of the tube. It is desirable to channel or steer as much light as possible downwardly through the tube to illuminate the building interior. One such approach includes positioning a reflector inside the dome above the roof to reflect light downwardly into the tube. A tubular skylight of this type is illustrated in U.S. Pat. No. 5,099,622, issued Mar. 31, 1992, to Sutton, and entitled xe2x80x9cSkylight.xe2x80x9d However, this approach is relatively complex structurally, relatively expensive, and aesthetically deficient. Further, the reflector may actually decrease the performance of the skylight when no direct sunlight is present, because the reflector blocks a portion of the ambient light.
The aforementioned problems are overcome in the present invention wherein the dome of a tubular skylight includes an exterior surface having a prismatic portion to reflect light downwardly into the tube. Preferably, the prismatic portion is located on the northern portion of the dome. Consequently, sunlight entering the southern portion, and to a lesser extent the eastern and western portions, of the dome at relatively low angles is reflected by the prismatic surface downwardly into the tube.
In the disclosed embodiment, the dome is hemispherical including a base and an apex. The prismatic surface includes a plurality of vertical grooves each extending between the base and the apex along great circles passing through the apex. The grooves begin at the base and terminate short of the apex. Further preferably, the grooves are located in an angular segment of the hemispherical dome.
The prismatic surface increases the amount of light directed or steered downwardly through the tube. The enhancement is most notable when the sun is relatively low in the sky as in the morning, the late afternoon and evening, and during the winter months. The dome also increases both the portion of the day and the number of seasons during which the skylight provides effective interior lighting.
These and other objects, advantages, and features of the invention will be more fully understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings.